Wire Size?

I'm going to be connecting a M1-ATX into my Morex 3688 case. As of right now I have 1/0 running from my battery to a fuse holder with a 250A fuse in it. From there, I have 1/0 running straight to my subwoofer amp in my back. What I'm going to do is add a fused distrobution block in the back and have 4 gauge coming from it to my amp and then I have no idea what size I should run to my M1-ATX? Does anyone have any idea? I did a search and came up with 22, 20, 18, and even 16 so I'm kind of lost on what to use.

Depending on the distance you have to run the wire I would say for up to 10 feet use 14 or 16 gauge. 8 gauge is pushing it. the m1atx can only pull around 10 amps and 14 gauge can easily handle that 8 gauge can handle up to 60 amps.